WILLSBORO -- They rise from the depths of Lake Champlain, four seemingly incongruous sentinels sitting miles from shore in one of the lake's widest sections.

They appear haggard from a distance, as if time itself has eroded their stately presence.

But Four Brothers Islands are teeming with life and play a major role in the breeding success of at least a dozen species of migratory birds.

"Our mission is biodiversity, and this is biodiversity in its glory," said Tom Berry, director of the Lake Champlain Program for the Adirondack Nature Conservancy and Land Trust, which owns the rights to Four Brothers Islands.

The islands don't have specific names but are called A, B, C and D, respectively, and possess distinct personalities of their own.

Islands A and B, which are farthest from the New York shore, are both capped with fairly thick growths of vegetation, while C and D are more or less bare, each possessing a strikingly different appearance.

GHOST SHIP ISLAND

Island D is perhaps the most distinctive, with the trunks of tall white pine trees still standing from one end to the other despite the fact that they died years ago.

"Island D had a huge white-pine canopy with a typical forest community underneath," said David Capen, research professor for the Rubenstein School of Environment and Natural Resources at the University of Vermont. "Island D would be the island where you'd land and pitch a tent if you were so inclined. It was truly a beautiful island."

Now, Island D looks eerily like a ghost ship, its masts rising from an earthen deck like huge matchsticks, devoid of branches, leaves and any sign of living vegetation.

The fate of those majestic trees lay in the island's popularity in attracting colonial birds to its shores. With large numbers of cormorants in particular breeding throughout the pine forest since arriving on Lake Champlain in the 1980s, the droppings from several generations eventually choked the life out of the pines.

A few great blue herons nest at the tops of those trees, but the most prevalent bird on the island continues to be the cormorant, a species that has drawn much attention of late, mostly because of what many see as a destructive nature on both vegetation and fish.

As Berry and Capen approached the southeastern corner of the island aboard Capen's UVM research vessel, dozens of young cormorants sat on the branches of the remaining trees, waiting for their parents to return with a tasty fish meal for them.

Many more remained hidden from sight, their nests placed wherever possible on the island's rocky ground.

"The cormorants came down here in greater numbers after Young Island was aggressively managed by Vermont," said Capen, who has been studying the flora and fauna of the island since the 1970s.

Young Island just north of the Grand Isle ferry crossing, he noted, had been a major location for breeding cormorants but is virtually free of them now. Vermont launched its management effort a few years ago, oiling eggs to prevent them from hatching as well as capturing and killing a certain percentage of adult cormorants.

RISING POPULATION

The birds didn't seem too keen on that effort, however, and abandoned Young Island for the friendlier environs of Four Brothers Islands.

The cormorant population on the islands more than doubled between 1998 and 2004 and has steadily risen since then to about 4,000 nests spread out on all four islands this year.

New York state has wanted to begin a cormorant-control program on Four Brothers Islands the past couple of years, but Nature Conservancy has balked at the idea in favor of studying the cormorants' impact on Lake Champlain more thoroughly.

This year, however, the owners agreed to a three-year management study, including the oiling of eggs.

"What we've been lacking is a lake-wide management plan," Berry said. "We've agreed to participate this year to help management agencies put together a lake-wide plan.

"We're not trying to eliminate cormorants from these islands," he added. "We're looking at management options to support the diverse community we have out there."

Earlier this year, Capen and staff members landed on islands A and B and oiled most of the eggs there.

They are hoping that a less-aggressive management plan will not chase the birds to another lake island.

In early July, as Capen and Berry cruised around the two dots of land, several adult cormorants could be seen perched on the trees that cover the two islands, but there were few young birds to be found.

"These adult birds will stay with these eggs until well into the season," Capen said.

It is probably too late to lay any more eggs this season, he said. If the eggs had been simply broken at the beginning of the season, adults would have laid new eggs to replace them.

Island A has a thick growth of basswood, and Island B, which the researchers call "the jungle," is covered with buckthorns. By oiling eggs on those islands and not the other two, researchers are hoping the adults will eventually choose islands C and D for their nests.

"With about 720 nesting pairs (on island A), you'd typically have 900 to 1,000 young birds leaving here," Capen said. "This year, you might have 100 young leave."

Each island is home to its own group of colonial species, including the three types of seagulls that breed on the lake, black-crowned night herons, great egrets, cattle egrets and Caspian terns.

The birds can often be seen mingling together. In fact, several black-crowned herons darted around the cormorant nests, snatching up fish that the young birds missed as their parents fed them.

That is another issue that has thrown a curve. Early in the year, Capen noticed that almost all of the fish that cormorants fed on were alewives, themselves a new aquatic species in Lake Champlain that people fear will have a negative impact on other fish species.

The Vermont Department of Fish and Wildlife, with permits to take a certain percentage of the cormorant population, is continuing its harvesting of the species by shotgun as another control method.

Those birds are being frozen and will be studied in the off-season to determine what kinds of fish they have been taking from the lake.

The water is quite shallow at some points between the four islands. In fact, the rocky bottom, covered with countless zebra mussels, can be seen from the shores of Island A and Island B.

Yet each mound of rocks and brush and trees is its own individual ecosystem. Visitors to the site are warned by signs to stay off the islands, though they can watch the environment in action from their boats.

jmeyers@pressrepublican.com

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